On Monday, U.S. Senators Herb Kohl and Mike Lee, Chairman and Ranking Member of the Judiciary Antitrust Subcommittee, sent a letter to Jon Liebowitz, Chairman of the Federal Trade Commission (FTC), expressing concerns over Google's business practices and its impact on competition in Internet search and commerce.

"We believe these allegations regarding Google's search engine practices raise important competition issues. We are committed to ensuring that consumers benefit from robust competition in online search and that the Internet remains the source of much free-market innovation. We therefore urge the FTC to investigate the issues raised at our Subcommittee hearing to determine whether Google's actions violate antitrust law or substantially harm consumers or competition in this vital industry," they stated in the letter.

The Senators letter notes that, "rather than act as an honest broker of unbiased search results, Google's search results appear to favor the company's own web products and services." They go on to suggest that "under the the FTC's mandate to protect consumers from misleading and deceptive practices, the FTC should seriously consider requiring Google to label its 'inbox' or 'places' listing (or other similiar listings), as Google products, just as it labels paid search results."

In September, Kohl and Lee convened a hearing of the Judiciary Antitrust Subcommittee to examine Google's effects on competition and heard testimony from Google's Executive Chairman Eric Schmidt and others.

The FTC is already on the case, having confirmed last summer that is investigating Google's business practices.

Nonprofit organization "Consumer Watchdog" has been also calling for antitrust action against the Internet giant since 2010.